I run one.
The stock buffer that came in my 16in gun is an H buffer with a Sprinco(White) regular carbine spring. This setup has performed really well with everything from 160gr @1050fps all the way to .45 Super 185gr @1600fps , 255gr @1200fps handloads for bowling pin comps and Hog hunting.
I did try a standard carbine 3oz buffer with the 160gr loads for a few USPSA matches with very good success, the recoil impulse was minimised. But this rifle already shoots so soft due to the radially delayed blowback .
Geissele SSA trigger, has worked really well in my rifle.
I run small primer Blaser or Fed brass and CCI 400 primers. Most factory loads will gain about 100-150fps in this 16in barrel , .45 SUPER will be quite a bit higher. (These guns are factory rated for .450 SMC and .45 SUPER)
If you want to go slow say 130pf, I would switch to a 3oz standard carbine buffer and ** POSSIBLY** a sprinco reduced recoil spring or one of the subsonic 300blk springs.
The Kriss 30rnd mag extensions have worked well as long as you have a Glock mag body that doesn't bulge (having a few mags to try helps a ton)
Techwell makes a Mag well and it is fantastic.
These are really great rifles and pretty awesome that you can make a ton of power with 45 Super if you want to.
I have about 4500rnds through mine of all types of bullet profiles and velocities. Semi-wadcutters are problematic in feeding as are some wide meplat hunting bullets. Round nose flat point and traditional fmjs work great. Truncated cone bullets work well as long as the oal is short.